Recently, the development of radiation-curable ink, which is cured by irradiation with ultraviolet light, electron beams, or any other kind of radiation, has been advanced. When radiation-curable ink is used to record information on ink-repellent media, which absorb no or little ink, such as plastics, glass, and coated paper, the ink is quick to dry and allows you to record the information while avoiding ink bleed. Radiation-curable ink contains a polymerizable monomer, a polymerization initiator, a pigment and other additives, and so forth.
Incidentally, recorded matter obtained by recording an image on polyethylene terephthalate resin, vinyl chloride resin, or any other kind of flexible recoding medium may be attached to an article having curved surfaces, such as a car body. In this application, recorded matter is usually elongated before being attached to the article, and thus it is desirable that even after the recorded matter is elongated, the image recorded on the recording medium has a degree of elongation equal to or higher than 100%, no cracks or detachment, and a degree of durability high enough to withstand the elongation at such a degree.
Known types of radiation-curable inks contain, for the purpose of allowing for recording flexible images with a degree of elongation equal to or higher than 100%, a polymerizable monomer such as a long-chain alkyl acrylate, phenoxyethyl acrylate, an ethylene oxide adduct of phenoxyethyl acrylate, and an acrylic amine compound (for example, see Patent Literature 1 to 4).
And, high-energy light sources that have been commonly used, such as metal halide lamps, have problems of their short shelf life, large size, and so forth. In particular, light sources that are incorporated in ink jet recording apparatuses are required to be small in size because of the constitution of the apparatuses. Recently, as a result, light-emitting diodes (hereinafter also referred to as LEDs), a long-life and small-sized light source, have attracted attention despite their lower energy than that of metal halide lamps.